Liquid ammonia flow meter

1) Structure

SBL flowmeter mainly consists of measurement tube (casing), stress element (target plate), sensing elements (force transducer, pressure transducer and temperature transducer), transition part (adjusted according to temperature and pressure), and accumulation calculation, display and output part. Refer to the following figure for the structure:

2) Operating principle

Refer to Fig.1 for operation schematic of model SBL target flowmeter with digital display. The stress element (target plate) is placed at center of measurement tube (instrument body) coaxially, with rigid connection with transducers. When measured medium flows at certain velocity (m/s), this medium has certain momentum that directly acts on the stress element (target plate). Due to rigid connection between stress element and transducer, the transducer is subject to direct force F generated by fluid momentum. This force is related to flow velocity V, medium density ρ and area of target subject A to force as follows:

In which:

F——force on target plate

C_D——resistance coefficient

P——fluid density, kg/m³

V——fluid velocity, m/s

A——area of target plate subject to force, m²

Through derivation and conversion, the flow is calculated as follows:

In which

Q_m, Q_V--mass flow and volume flow respectively (kg/h, m³/h)

α----flow coefficient

D----inner diameter of measurement tube, mm

β----diameter ratio, β=d/D

d----target plate diameter, mm

Other symbols are the same before.

Force on target plate is converted to electric signal by the force transducer. This signal is amplified by pre-amplification and processed by AD conversion and computer, to provide corresponding flow and total quantity. Operating principle is shown as follows: